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Apr 28, 2018, 02:14 PM
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Building a Keil Kraft Radian with a Cox TeeDee O51


I have just started to build a Keil Kraft Radian with a Cox TeeDee 051 (I have just about got all the materials together to start.

Just wondered if anyone has any experience in using a TeeDee 049/051 in a 1/2A stunter and can give me any advice on the best set-up? Do I need to modify my Mercury 10cc wedge tank to a "uniflow" type arrangement?

(Yes, I know I would be better off starting with at least a 15 size model...)

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Apr 28, 2018, 03:44 PM
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Hi Matthew,

I have no answers for you. Is this the $60 eBay kit, or scratch-build?

I've been watching the eBay kit for a couple while. If I ever get caught up with my stash, then this one is the first full-fuse plane I want. Or I may scratch build a Challenger.

Having said that, you have at least one fan and wanting to watch the build!

Good luck with away!
Apr 28, 2018, 04:08 PM
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Thanks for the encouragement; this one is being made from the Outerzone plan (though from my experience with the Vintage Model Company's KK Elf their KK Radian kit is probably excellent, and as kits go good value for money). However, I will be making a few additions and mods to mine i.e. adjustable lead-outs and removeable engine mounts in case I want to put my PAW 06 BR in it...

Will post the odd build photo, especially where I have deviated - I think we now have much better ways of doing things than we did in the early 60s.
Apr 28, 2018, 06:28 PM
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Thanks for answering back!

While it goes together, can you watch for room for a 3-line bellcrank? Is the wing thick enough? Could one be mounted in the fuselage?

Either the Radian, or the WM Challenger are what I'm considering for a throttled Norvel Big Mig .061. The Challenger may be big enough for an AP .09, although smaller planes fit my "hanger space" better.

I'll be glad to push any measurements/pics concerning J Roberts3-line bellcranks. I have one each top-mount hanger and bottom-mount upright unit...and instructions.

Watching from the side cheering you on!
Apr 29, 2018, 10:53 AM
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Since I have only recently been sucked into CL, but have always wanted a Radian since seeing the kit box as a child, I am probably going to avoid the complexity and drag of third line throttle control - though I am interested in any info you can pass on regarding the J Roberts 3 line bellcranks.

It should be remembered that the KK Radian is a very small plane - only 22" span with a max depth of wing rib of approx 22mm, with a max of 6mm inside fuselage depth beneath the wing at max section depth, and up to 15mm fuselage depth above the wing; internal fuselage width is approx 34mm.

I suspect that no-one has ever achieved useable 4-2-4 engine cycling with a .049...

I am taking a lot of my trimming and adjustment advice from the website; since I have not flown any CL since my KK Phantom Mite with a DC Wasp (only ever went round and round); I will probably slap together and fly an all sheet 1/2A Nobler from Den's Models after I have finished the Radian.

BTW I tend to build stuff because I like the shape/concept, but tend to go off plan when re-engineering the mechs and sorting out the dynamics (see my finally finished Pegasus Models Gold Cloud 100S glider in the Thermal section). In short, most people will get in the more quickly in the air with a lighter/cheaper model than if they follow the way I go about it.
Apr 30, 2018, 05:18 AM
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If you can, scale up the KK Radian plan to 26inches... a TD051 is nearly twice to power of the little reed valve 049 in the video.. you will have a team racer, not a stunter

The Pinto, teedee049 stunt model is 34inches wingspan.

I really do think 22inches is too small for your TD051 engine!
Last edited by Azryl; Apr 30, 2018 at 05:29 AM. Reason: additional information
Apr 30, 2018, 04:54 PM
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I completely agree with you regarding the power to wing area issue, but, for nostalgic reasons I will try to keep the original shape as much as possible. There are mitigating factors though: - here in the UK getting fuel with more than 25% nitro-methane is tricky; by the time I have added castor oil to Model Technics' Big Bang 25 fuel, the nitro percentage will be a little bit lower. Plus, I intend to run on 42' 20 pound Kastking braided line (done the pull test).

I will probably run the TeeDee a little rich but well within its comfort rpm, take-off at a bit over 17000 rpm but won't tune for all out power. Were you looking at the Radian being flown by "Andy Modeller" - looked to me he had very short lines and not much power.

However, I really like the look of that Pinto - a new home for my brand new PAW 06BR?
May 14, 2018, 06:09 PM
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What goes into a KK Radian...

Just to show that I am actually going to do this, here are some fuzzy pictures of the bits cut-out using the templates from the Outerzone plan. Pretty much all the materials/pieces are here except for the control horns which I will make from G10; and a few additional changes that I am going to make around the lead-outs (I will make them adjustable) and bell-crank.

I suspect that the Vintage Model Companies kit of the Radian is very good value for money and allows for a very accurate and light model to be built very quickly. I would be very interested to see a build log of said kit.
May 14, 2018, 11:57 PM
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Looking really good there! I've been wondering and checking. Glad to see forward progress. Good for you!
May 19, 2018, 07:43 PM
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I have been a bit slow on the build, since I have been playing with my refurbished Cox Engines and PAW 06BR - flying electric RC has made me very lazy, much more effort to fly IC.

Also, making the Paxolin engine mount (dubious logic for doing this modification) and adjusting everything to suit has slowed down progress on the build a little. All said, this aircraft could be made very quickly by anyone who had interest in doing so.

Should post some more photos soon.
Jun 08, 2018, 10:19 PM
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Got an original one of those in the basement, still in the shrink wrap! Was a model I always wanted as a kid. Don't know if I'll ever get around to building it.
Aug 14, 2018, 07:22 PM
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Just to let you know have not abandoned the Radian build - have been doing a lot of flying this year with incredibly hot summer we are having in the UK (stay out of the sun as much as possible and use sun cream - I am being serious here).

However have nearly got ready a Black Hawk Models' 1/2A Nobler to serve a my stunt trainer - much more wing area than the Radian.
Aug 14, 2018, 09:08 PM
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Seeing you have a full bodied plane, this is going to prove worthy using the TD on suction. Make certain your TD has a stock venturi and that no one drilled it larger for more performance. The TD wants to run fast. I personally would modify the tank for uniflow as it's beneficial to the run and will assist in a persistent fuel draw. A standard vent tank is going to run lean throughout the run , therefore at some point possibly half way through the tank the engine is going to take off like a bullet. More than likely it will run this way until the end. You don't have to use the high compression head which will offer a slight advantage to the run your trying to achieve. Keeping fuel delivery is imperative to the run your looking to achieve. One option is to use 3-4 head gaskets as this will lower the compression and keep it cycling opposed to breaking lean and staying there. The TD is pretty thirsty therefore rather than trying to regulate the speed using the needle which is not always a good idea I would experiment with props. The TD is not exactly happy on 6" props, this doesn't mean they won't work, it just likes the higher rpm's so using smaller props say 5" might be in order.

The TD can be a bit cantankerous when you try and run it richer. The setting isn't consistent and it likes to shut off. I think it has a tendency to load up with fuel therefore leaning it out prevents this. Your better bet would be a Medallion .049 but seeing this is what you have, I would certainly try it. I think you will be successful using additional head gaskets as this does keep it out of it's maximum power band and you can still run with the proper setting. The TD comes stock with the high comp 1702 glow head, you can use the Cox 325 standard plug which also tames the engine run down,
Aug 15, 2018, 04:37 PM
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Thread OP

Thanks for this advice; my plan was to do pretty much as you recommend; but I did not think of lowering the compression in the TeeDee 051 to get the desired speed (I now have all the spares).

I am looking to get one or two more TeeDee 049/051 to ensure airtime but there does not seem to be many cheap second hand ones going around in the UK anymore - I don't want boxed pristine examples that are too valuable to fly...

Also, has anyone recently had dealings with NV Engines (formerly Norvell Engines) - I would like to buy a new BigMig 061, but I cannot seem to get registered on their website?!
Sep 30, 2018, 05:21 PM
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Radian Build Restarted

Just to show that this build has not been forgotten.

I will probably have fuel economy issues with that 10cc wedge tank though...

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